444 



OPTICAL PROJECTION 



FER 



INV 



Ferguson, Prof., and chemical 

 apparatus, 245 



Figures, Lissajous', 255, 258 



Films, thin, colours of, 324 ; soap, 

 225, 326 ; and electric currents, 

 408 ; crossed for polarising, 355, 

 382 



Flames, manometric, 2G9 ; sensi- 

 tive, 270 



Flashing on effects, 122 



Fluorescence, 317 



Focus of a lens, 5 ; and size of 

 image, 7, 30, 112 ; of lantern 

 objectives, 113 



Focussing lenses, loose for project- 

 ing, 175 



Forces, parallelogram of, 217 



Forks, vibrations of, 253, 25S 



Formulas for lantern distances, 

 discs, and foci, 112 



Four-way tap, 121 



Fox's mica preparations, 355 



Frame, rotating, 348 



Frames for portable screens, 131 



Fresnel's bi-prism, 332 



Fringes, interference, 332 



Frog, circulation in, 205 



Fronts, of lanterns, 32 ; optical, 

 171 



Fuchsine, dispersion of, 295 



GALVANOMETERS, and use, 400 

 Gas-bags, 42 ; cylinders, 82 

 Gas-burners, 40, 178, 418 

 Gas-supply, nozzles for, 47 

 Gases, phenomena of, 229 

 Gasoline for O.-H. light, 100 

 Gauze, diffraction by, 335 

 Gelatine for diagrams, 413 

 Generators for ether light, 92, 95 

 German model lantern, 153 

 Glass, compressed or heated, 360 ; 



sounded, 362 

 Glass polarising apparatus, 340, 



345 



Glasses for acoustics, 249 

 Gratings, diffraction, 334 

 Gravett's condenser, 18 

 Gravitation, 220 



Ground-glass, drawings on, 413 

 Giilcher arc-lamp, 103 



HALOS, projection of, 335 



Hardwich, Eev. F., and ether light, 

 93 



Harmonic vibrations, 252, 267 



Hawkridge's vertical lantern, 168 



Heart, movements of, 235 



Heat. 385 ; identity with light, 

 392 ; in the microscope, 183 



Hepworth, Mr., on stand for the 

 lantern, 133 



Herschel condenser, 18 



Highley, Mr., on jets, 47, 67 



Hopkins, G. M., electrical experi- 

 ments, 399 



Huygen's apparatus and experi- 

 ment, 349 



Hydrogen, preparation of, 73 



Hydrostatics, 221 



ICELAND spar, scarcity of, 345 

 Illuminating power of spirit jets, 

 47 ; oxy-gas jets, 50 ; mixed 

 jets, 62 ; arc light, 164 

 Image-forming power of all light- 

 rays, 2, 274 



Image, microscopic, in demonstra- 

 tion, 190 



Images, not formed by lenses, 1 ; 

 inversion of, 3, 6, 215 ; relative 

 size of, 3 



Immersion micro-objectives, 195 

 Incandescent lamp, 40, 41, 418 ; 

 projection of, 409 ; spirit burner, 

 418 



Inches of gas-pressure, 54 

 Inclination of nipple and lime in 



jets, 67 

 Induction, magnetic, 395 ; static, 



396 ; current, 402 

 Institutions and screens, 124, 126 

 Interference of light, 321 ; of 



polarised light, 352 ; heat, 393 

 Inversion of images, 215 

 Invisible spectrum, the, 315 



